Parasites, such as helminths, are found in many animals, particularly grazing animals, and are responsible for significant economic losses throughout the world. Among the helminths most frequently encountered in grazing animals such as cattle, horses, goats and sheep are trematodes, i.e., flukes, for instance, Fasciola hepatica, and nematodes such as Haemonchus contortus. A valuable tool for the treatment of homeothermic animals suffering from such parasites is closantel (U.S. Pat. No. 4,005,218 and Merck Index, 13th Edition).
Closantel is known to demonstrate little or no capacity for transdermal penetration at present, so the most effective means of administering closantel involves parenteral or oral administration. Commercially, Closantel is sold as its sodium salt, under Flukiver® for subcutaneous administration and Seponver® as an oral drench. Although the use of the sodium salt of closantel in a topical liquid composition is described in WO 97/13508, there still remains a need for closantel compositions which exhibit improved transdermal penetration properties, as well as increased bioavailability. It is apparent that, not withstanding high safety margins, a lower but effective dosage is always preferred.
Therefore, it is an object of this invention to provide improved antiparasitic compositions which, when administered to a homeothermic animal, increase the levels of closantel in the blood of said animal.
It is another object of this invention to provide a method for the enhanced protection of a homeothermic animal from parasitic infection.
It is a feature of this invention that the improved antiparasitic compositions may be administered to a homeothermic animal by topical, as well as parenteral, application, and whether alone, or in combination, with other antiparasitic compounds.